The invention relates generally to a method and apparatus for applying energy to shrink a hollow anatomical structure, such as a fallopian tube or a vein, including, but not limited to, superficial and perforator veins, hemorrhoids, and esophageal varices, and more particularly, to a method and apparatus using an electrode device having multiple leads for applying radio frequency (RF) energy, microwave energy, or thermal energy.
The human venous system of the lower limbs consists essentially of the superficial venous system and the deep venous system with perforating veins connecting the two systems. The superficial system includes the long or great saphenous vein and the short saphenous vein. The deep venous system includes the anterior and posterior tibial veins which unite to form the popliteal vein, which in turn becomes the femoral vein when joined by the short saphenous vein.
The venous system contains numerous one-way valves for directing blood flow back to the heart. Venous valves are usually bicuspid valves, with each cusp forming a sack or reservoir for blood which, under retrograde blood pressure, forces the free surfaces of the cusps together to prevent retrograde flow of the blood and allows only antegrade blood flow to the heart. When an incompetent valve is in the flow path, the valve is unable to close because the cusps do not form a proper seal and retrograde flow of the blood cannot be stopped. When a venous valve fails, increased strain and pressure occur within the lower venous sections and overlying tissues, sometimes leading to additional valvular failure. Two venous conditions which often result from valve failure are varicose veins and more symptomatic chronic venous insufficiency.
The varicose vein condition includes dilation and tortuosity of the superficial veins of the lower limbs, resulting in unsightly discoloration, pain, swelling, and possibly ulceration. Varicose veins often involve incompetence of one or more venous valves, which allow reflux of blood within the superficial system. This can also worsen deep venous reflux and perforator reflux. Current treatments of vein insufficiency include surgical procedures such as vein stripping, ligation, and occasionally, vein-segment transplant.
Chronic venous insufficiency involves an aggravated condition of varicose veins which may be caused by degenerative weakness in the vein valve segment, or by hydrodynamic forces acting on the tissues of the body, such as the legs, ankles, and feet. As the valves in the veins fail, the hydrostatic pressure increases on the next venous valves down, causing those veins to dilate. As this continues, more venous valves will eventually fail. As they fail, the effective height of the column of blood above the feet and ankles grows, and the weight and hydrostatic pressure exerted on the tissues of the ankle and foot increases. When the weight of that column reaches a critical point as a result of the valve failures, ulcerations of the ankle begin to form, which start deep and eventually come to the surface. These ulcerations do not heal easily because of poor venous circulation due to valvular incompetence in the deep venous system and other vein systems.
Other related venous conditions include dilated hemorrhoids and esophageal varices. Pressure and dilation of the hemorrhoid venous plexus may cause internal hemorrhoids to dilate and/or prolapse and be forced through the anal opening. If a hemorrhoid remains prolapsed, considerable discomfort, including itching and bleeding, may result. The venous return from these prolapsed hemorrhoids becomes obstructed by the anal sphincters, which gives rise to a strangulated hemorrhoid. Thromboses result where the blood within the prolapsed vein becomes clotted. This extremely painful condition can cause edema and inflammation.
Varicose veins called esophageal varices can form in the venous system with submucosa of the lower esophagus, and bleeding can occur from the dilated veins. Bleeding or hemorrhaging may result from esophageal varices, which can be difficult to stop and, if untreated, could develop into a life threatening condition. Such varices erode easily, and lead to a massive gastrointestinal hemorrhage.
Ligation of a fallopian tube (tubal ligation) for sterilization or other purposes is typically performed by laparoscopy. A doctor severs the fallopian tube or tubes and ties the ends. External cauterization or clamps may also be used. General or regional anesthetic must be used. All of the above are performed from outside the fallopian tube.
Hemorrhoids and esophageal varices may be alleviated by intra-luminal ligation. As used herein, xe2x80x9cligationxe2x80x9d or xe2x80x9cintra-luminal ligationxe2x80x9d comprises the occlusion, collapse, or closure of a lumen or hollow anatomical structure by the application of energy from within the lumen or structure. As used herein, xe2x80x9cligationxe2x80x9d or xe2x80x9cintra-luminal ligationxe2x80x9d includes electro-ligation. In the case of fallopian tube ligation, it would be desirable to perform the ligation from within the fallopian tube itself (intra-fallopian tube) to avoid the trauma associated with external methods.
Ligation involves the cauterization or coagulation of a lumen using energy such as that applied through an electrode device. An electrode device is introduced into the lumen and positioned so that it contacts the lumen wall. Once properly positioned, RF energy is applied to the wall by the electrode device thereby causing the lumen to shrink in cross-sectional diameter. In the case of a vein, a reduction in cross-sectional diameter of the vein, for example from 5 mm (0.2 in) to 1 mm (0.04 in), significantly reduces the flow of blood through a lumen and results in an effective occlusion. Although not required for effective occlusion or ligation, the vein wall may completely collapse thereby resulting in a full-lumen obstruction that blocks the flow of blood through the vein. Likewise, a fallopian tube may collapse sufficient to effect a sterilization of the patient.
One apparatus for performing ligation includes a tubular shaft having an electrode device attached at the distal tip. Running through the shaft, from the distal end to the proximal end, are electrical leads. At the proximal end of the shaft, the leads terminate at an electrical connector, while at the distal end of the shaft the leads are connected to the electrode device. The electrical connector provides the interface between the leads and a power source, typically an RF generator. The RF generator operates under the guidance of a control device, usually a microprocessor.
The ligation apparatus may be operated in either a monopolar or bipolar configuration. In the monopolar configuration, the electrode device consists of an electrode that is either positively or negatively charged. A return path for the current passing through the electrode is provided externally from the body, as for example by placing the patient in physical contact with a large low-impedance pad. The current flows from the ligation device through the patient to the low impedance pad. In a bipolar configuration, the electrode device consists of a pair of oppositely charged electrodes of approximately equal size, separated from each other, such as by a dielectric material or by a spatial relationship. Accordingly, in the bipolar mode, the return path for current is provided by an electrode or electrodes of the electrode device itself. The current flows from one electrode, through the tissue, and returns by way of the oppositely charged electrode.
To protect against tissue damage; i.e., charring, due to cauterization caused by overheating, a temperature sensing device is attached to the electrode device. The temperature sensing device may be a thermocouple that monitors the temperature of the venous tissue. The thermocouple interfaces with the RF generator and the controller through the shaft and provides electrical signals to the controller which monitors the temperature and adjusts the energy applied to the tissue through the electrode device accordingly.
The overall effectiveness of an ligation apparatus is largely dependent on the electrode device contained within the apparatus. Monopolar and bipolar electrode devices that comprise solid devices having a fixed shape and size can limit the effectiveness of the ligating apparatus for several reasons. Firstly, a fixed-size electrode device typically contacts the vein wall at only one point on the circumference or inner diameter of the vein wall. As a result, the application of RF energy is highly concentrated within the contacting venous tissue, while the flow of RF current through the remainder of the venous tissue is disproportionately weak. Accordingly, the regions of the vein wall near the point of contact collapse at a faster rate then other regions of the vein wall, resulting in non-uniform shrinkage of the vein lumen which can result in inadequacy of the overall strength of the occlusion and the lumen may eventually reopen. To avoid an inadequate occlusion, RF energy must be applied for an extended period of time so that the current flows through the tissue generating thermal energy including through the tissue not in contact with the electrode to cause that tissue to shrink sufficiently also. Extended applications of energy have a greater possibility of increasing the temperature of the blood to an unacceptable level and may result in a significant amount of heat-induced coagulum forming on the electrode and in the vein which is not desirable. This can be prevented by exsanguination of the vein prior to the treatment, and through the use of temperature regulated power delivery.
Secondly, the effectiveness of an ligating apparatus having a fixed-size electrode device is limited to certain sized veins. An attempt to ligate a vein having a diameter that is substantially greater than the electrode device can result in not only non-uniform heating of the vein wall as just described, but also insufficient shrinkage of the vein diameter. The greater the diameter of the vein relative to the diameter of the electrode device, the weaker the energy applied to the vein wall at points distant from the point of electrode contact. Accordingly the vein wall is likely to not completely collapse prior to the venous tissue becoming over cauterized at the point of electrode contact. While coagulation as such may initially occlude the vein, such occlusion may only be temporary in that the coagulated blood may eventually dissolve recanalizing the vein. One solution for this inadequacy is an apparatus having interchangeable electrode devices with various diameters. Another solution would be to have a set of catheters having different sizes so that one with the correct size for the diameter of the target vein will be at hand when needed. Such solutions, however, are both economically inefficient and can be tedious to use. It would be desirable to have a single catheter device that is usable with a large range of sizes of lumina.
Although described above in terms of a vein, the concepts are generally applicable to other hollow anatomical structures in the body as well. For consideration of avoiding unnecessary repetition, the above description has been generally confined to veins.
Hence those skilled in the art have recognized a need for an expandable electrode device and a method capable of more evenly distributing RF energy along a circumferential band of a wall of the target anatomical structure where the wall is greater in diameter than the electrode device, and thereby provide more predictable and effective occlusion of anatomical structures while minimizing the formation of heat-induced coagulum. Such device and method should be applicable to the ligation of all the veins in the body, including but not limited to perforator and superficial veins, as well as hemorrhoids, esophageal varices, and also fallopian tubes. The invention fulfills these needs and others.
Briefly, and in general terms, the present invention provides an apparatus and method for applying energy along a generally circumferential band of the wall of a hollow anatomical structure, such as a vein, fallopian tube, hemorrhoid, or esophageal varix. The application of energy in accordance with this apparatus and method results in a more uniform and predictable shrinkage of the structure.
In a first aspect, an apparatus for applying energy to a hollow anatomical structure comprises a catheter having a shaft with a working end at which energy is applied to the structure, a first plurality of expandable electrode leads mounted at the working end of the catheter, each lead having an electrode, a second plurality of expandable electrode leads mounted at the working end of the catheter separate from and longitudinally spaced apart from the first plurality and longitudinally spaced apart from the first plurality, each lead having an electrode, wherein electrodes of the first and second pluralities each have an expanded position at which the electrode is located outward from the catheter shaft and a contracted position at which the electrode is located nearer the shaft, and a deployment device mounted to the catheter, the deployment device having a first position at which selected electrodes are in the contracted position and a second position at which electrodes are in the expanded position. In more detailed aspects, the electrode leads of the first plurality are formed such that they are urged outwardly from the catheter shaft, wherein the deployment device comprises a movable sheath having a first position at which the sheath surrounds the first plurality of electrode leads over at least a portion thereof and confines the surrounded leads to a contracted position, the movable sheath having a second position at which the first and second pluralities are permitted to expand outwardly. Further, the electrode leads of the second plurality are formed such that they are urged outwardly from the catheter shaft. The movable sheath at its first position also surrounds the second plurality of electrode leads over at least a portion thereof and confines the surrounded leads to a contracted position.
In further aspects, each of the electrode leads of the first and second pluralities is formed with an outward bend that tends to expand the distal portion of each lead outwardly with the second plurality of electrode leads mounted to the catheter proximal to the first plurality, the movable sheath at its first position in relation to the electrode leads is distal to the bends of the first and second pluralities of electrode leads thereby retaining the first and second pluralities in contracted configurations. The movable sheath at its second position is proximal to the bends of the first and second pluralities thereby permitting the first and second pluralities to expand outwardly.
In yet further detailed aspects, the electrode leads are mounted at the working end in a cantilever arrangement. Each of the electrode leads of the first and second pluralities are disposed in relation to the working end such that when in the expanded position, the electrodes of the leads form a substantially symmetric arrangement of substantially evenly-spaced electrodes. Each electrode lead is formed of an electrically conductive material insulated along its length, and each electrode lead includes an outwardly-facing portion at which no insulation is present thereby forming the electrode. The electrode leads are formed of a material having a strength selected such that when the sheath is in its second position, the leads are strong enough to move into apposition with the hollow anatomical structure, and the leads have a strength such that they permit the hollow anatomical structure to shrink but remain in apposition with the shrinking structure.
The first plurality of electrode leads are mounted to a first electrically-conductive mounting ring to which the electrodes of those leads are electrically inter-connected. The second plurality of electrode leads are mounted to a second electrically-conductive mounting ring to which the electrodes of those leads are electrically inter-connected. A third electrically-conductive mounting ring is provided to which alternating electrode leads of a selected one of the pluralities of electrode leads are connected thereby resulting in adjacent leads of the selected plurality being connected to different mounting rings. A power source is connected to the electrodes and a controller controls the power source. A switch is connected to the controller, the switch having a first position at which the controller applies different polarities to the mounting rings, and a second position at which the controller applies the same polarity to the mounting rings.
In yet another aspect, a power source is connected to the electrodes, a controller controls the power source, and a temperature sensor is mounted to an electrode lead, the temperature sensor providing temperature signals to the controller wherein the controller controls the power source in response to the temperature signals.
In further aspects, the controller is adapted to switch the electrical polarity of the leads as selected including controlling the output of the power source to the electrode leads such that adjacent electrodes of the first plurality of leads are of opposite polarities while maintaining the polarity of the second plurality of electrodes so that they are electrically neutral, switching the polarity of the electrodes of the first plurality of leads so that they are all of the same polarity upon collapse of the hollow anatomical structure around the first plurality of leads, and controlling the power source so that the electrodes of the second plurality of leads are of opposite polarity relative to the electrodes of the first plurality of leads upon performing the step of switching the polarity of the electrodes. The controller is further adapted to, in more detailed aspects, control the power source so that adjacent electrodes of the first plurality are of opposite polarity, control the power source so that adjacent electrodes of the second plurality are of opposite polarity, and control the power source so that the polarities of the electrodes of the second plurality are selected so that opposite polarities are longitudinally aligned with the electrodes of the first plurality. In yet further aspects, the apparatus further comprises a backplate located at a surface of the patient wherein the controller is further adapted to control the energy applied to one of the pluralities of electrode leads so that the electrodes are of a first polarity and control the energy applied to the backplate so that it is a second polarity.
In another aspect, the deployment device comprises a movable sheath and an alignment device positioned inside the sheath, the alignment device maintaining separation between the electrode leads wherein movement of the sheath and alignment device in relation to each other controls whether the electrode leads are expanded or contracted.
In accordance with other method aspects of the invention, there is provided the steps of introducing into the hollow anatomical structure a catheter having a shaft and a working end with a first plurality of electrode leads disposed at the working end and a second plurality of electrode leads disposed at the working end spaced longitudinally apart from the first plurality, each lead having an electrode connected to a power source, expanding leads of the first plurality outwardly from the working end of the catheter wherein the electrodes of the first plurality move away from each other and into contact with the inner wall, and expanding the leads of the second plurality outwardly from the working end of the catheter, wherein the electrodes of the second plurality move away from each other and into contact with the inner wall at positions spaced apart longitudinally from the contact points on the inner wall of the first plurality. Further, in another aspect, the method comprises the step of applying energy to the inner wall from electrodes of the electrode leads to collapse the hollow anatomical structure to effectively occlude the hollow anatomical structure.
A more detailed aspect includes the step of moving a sheath and the first and second pluralities of electrodes in relation to each other to selectively expand the electrode leads outwardly or contract the electrode leads.
The method further comprises the step of moving the catheter in the hollow anatomical structure while continuing to apply energy to the hollow anatomical structure by the electrodes. Additionally, the step of compressing the hollow anatomical structure to a desired size before and/or during the step of applying energy is provided. Further steps comprise compressing the hollow anatomical structure with a tourniquet or elastic bandage before and/or during the step of applying energy and monitoring the hollow anatomical structure through an ultrasound window formed in the tourniquet or bandage. More detailed aspects of the method comprise exsanguinating the hollow anatomical structure before and/or during the step of applying energy, by delivering fluid to displace blood from the anatomical structure, or by compressing the hollow anatomical structure.
In addition, there are provided the steps of controlling the energy applied to the electrodes of the first plurality of leads so that they have a first polarity and controlling the energy applied to the electrodes of the second plurality of leads so that they have a second polarity different from the first polarity. In another aspect, provided are the steps of controlling the power source so that adjacent electrodes of the first plurality of leads are of opposite polarity while maintaining the polarity of the second plurality of electrodes so that they are electrically neutral, switching the polarity of the electrodes of the first plurality of leads so that they are all of the same polarity upon collapse of the hollow anatomical structure around the first plurality of leads, and controlling the power source so that the electrodes of the second plurality of leads are of opposite polarity relative to the electrodes of the first plurality of leads upon performing the step of switching the polarity of the electrodes.
Further aspects include applying a backplate to a surface of the patient, controlling the energy applied to one of the pluralities of electrode leads so that the electrodes are of a first polarity, and controlling the energy applied to the backplate so that it is a second polarity. In another aspect, the method comprises the steps of controlling the power source so that adjacent electrodes of the first plurality are of opposite polarity, controlling the power source so that adjacent electrodes of the second plurality are of opposite polarity, and controlling the power source so that the polarities of the electrodes of the second plurality are selected so that opposite polarities are longitudinally aligned with the electrodes of the first plurality.
In yet further detailed aspects, a method comprises the steps of sensing the temperature at an electrode lead and controlling the application of power to the electrode leads in response to the temperature sensed at the lead. Additionally, there is provided the step of flushing the hollow anatomical structure with fluid before the step of applying energy.
Further aspects include introducing a catheter having first and second pluralities of longitudinally, spaced-apart expandable electrode leads into a vein, introducing the catheter into a fallopian tube, introducing the catheter into a hemorrhoid, or introducing the catheter into an esophageal varix.
These and other aspects and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings which illustrate, by way of example, embodiments of the invention.